How do u define this <u|A|u>? where A is a selfadjoint linear operator.(adsbygoogle = window.adsbygoogle || []).push({});

I have one book that defines is as ||A|u>||^2=<u|A|u>

(equation 2.6 http://www.theory.caltech.edu/people/preskill/ph229/notes/chap2.ps)

and since ||A|u>||^2 is the lenght of the vector A|u> squared that is equal to (<u|A)(A|u>).

I have another book (j.j sakurai) that defines it as (<u|)(A|u>)=(<u|A)(|u>)=<u|A|u> but this is the projection of A|u> on |u>.

It seems to me that the two definitions arent equal !? Any ideas?

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# <u|A|u> ?

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